I had two 30 minute long technical questions related to the fundamentals behind circuit design and past experience. The interviewers were respectful and asked very open ended questions so a lot of what I was asked needed justification on my choices.

One phone interview for 45min. The guy directly jumped into the resume with lots of technical questions. I'm in heat transfer and fluid areas so some general theory questions like: What is Reynolds number? What's the physical meaning of Reynolds number? How do you describe Reynolds number to someone with no fluid mechanics background. For heat transfer it was heat conduction equation, like what material properties do you need to solve a steady-state heat conduction equation? What if it is not a steady-state process?